1. Field of the Invention
The present disclosure relates to a downlink data transmission/reception technique for supporting a low-complexity User Equipment (UE) category/type for a Machine-Type Communication (MTC) operation, and more particularly to a technique for an MTC UE to transmit and receive a random access response.
2. Description of the Prior Art
Machine-Type Communication (hereinafter, referred to as “MTC”) is a type of data communication, which refers to device-to-device or machine-to-machine communication in which one or more entities do not necessarily involve human interaction. MTC involving no human interaction refers to any mode of communication that is achieved without human intervention in a communication process.
An MTC User Equipment (UE) may be installed in a place with a poor propagation environment as compared with a typical UE. In order for the MTC UE to operate in the poor propagation environment as compared with that for the typical UE, the MTC UE may need to repeatedly transmit control information and/or data on each physical channel, which is transmitted via only one subframe unit, via a plurality of subframes.
Further, the MTC UE may be restricted in using radio resources. That is, the MTC UE may be set to use only some frequency resources or some time resources.
As described above, the MTC UE is different from the legacy typical UE in the methods of transmitting and receiving data, and such a difference may make it difficult to achieve a random access procedure between the MTC UE and a base station. For example, due to repeated transmissions by the MTC UE, there is a possibility that the base station is restricted to process a very limited number of random access responses. Further, when the base station transmits random access responses to a plurality of MTC UEs, collision is increasingly likely to occur due to repeated transmissions.
Due to the foregoing problems, an initial random access procedure between the MTC UE and the base station may not be properly achieved.